This invention relates generally to sensor apparatus incorporating semi-permeable membranes, for use in measuring a predetermined parameter of a fluid sample and, more particularly, to sensor apparatus of this kind having means for sealing the fluid sample.
Sensor apparatus of this particular kind are useful in measuring a multitude of parameters of various fluid samples, including for example the measuring of glucose concentration in whole blood. Such sensor apparatus typically include a body or housing having a cavity in which is located an electrode assembly having one or more electrodes and further having a special semi-permeable membrane overlaying the electrodes and separating the electrodes from the fluid sample. The electrodes typically are located on a convex surface of the electrode assembly, and various structures have been used in the past to tension the membrane across the convex surface, in intimate contact with the electrodes. Such intimate contact is important in establishing a rapid response time.
The sensor apparatus described briefly above have, in most instances, functioned satisfactorily in providing reliable measurements of parameters such as glucose concentration in a liquid sample. However, the apparatus are not believed to have been entirely effective in sealing a chamber that carries the sample. This can be a serious deficiency in cases where the sensor apparatus is intended to be stored for an extended period while carrying a particular liquid sample in the chamber, and/or in cases where the chamber must be isolated from the external environment, to maintain the sample's sterility.
It should therefore be appreciated that there is a need for an improved sensor apparatus of the kind that incorporates a semi-permeable membrane overlaying an electrode assembly, for measuring a predetermined parameter of a fluid sample, where the apparatus is configured to more effectively ensure an intimate contact between the membrane and the electrode assembly and where the apparatus is configured to more effectively seal the sample from the external environment. The present invention fulfills this and other needs.